Are you the one who can't code? If this is the situation i suggest you to look for some WP template which is similar to the designed one. Try to change the images. After this, i guess setting the color codes, and the different width and height attributum in the css won't cause any problem.

I tell you a secret. Download all the files in template folder and then change what you want to change. After backing up, upload your template again. I have edited header of mine in this way and it is working very fine.